The present invention relates generally to a uniquely constructed stud which is ultrasonically insertable into a strip or segment of plastic material and a unique and novel method for ultrasonically inserting articles into such a strip or segment. The invention more specifically relates to a stud having a unique configured head which can be ultrasonically inserted into a strip of material to attain a pre-formed configuration comprised of a plurality of studs, and a novel method for ultrasonically inserting those studs into the strip or segment.
The inserting and embedding of a stud in a strip of plastic material is well known. For instance, the patent to Murdock et al., U.S. Pat. No. 2,860,082, discloses one way for embedding a plurality of studs in a protective body or strip. This method requires a preformed strip in which to insert the studs, and also requires the utilization of a substrate and glue-like combination in order to seal and fix the studs within the strip.
Utilization of this method may not be attractive to some because it does not allow for easy alteration of the stud configuration in the strip. To change the stud configuration, an entirely new strip must be machined, adding the significant costs of retooling. Also, the use of the substrate and glue-like combination can be messy as well as costly. Additionally, because of the multiple steps in the method, and the multiple parts in the construction, the Murdock method can be time consuming and labor intensive, thereby adding to the cost of utilization.
Alternative methods for inserting and encapsulating studs in a strip of material are available. Some of those methods produce constructions similar to that disclosed and illustrated in the patent to Egner, U.S. Pat. No. 294,676, and the patent to Ryder, U.S. Pat. No. 4,753,560. Many of these methods employ the techniques of injection or insert molding of the plastic material about the studs. These methods are quite expensive due to the high priced machinery required, and also provided some of the same, above-detailed drawbacks. For instance, to change the configuration of the studs on the strip, a new mold must be machined, resulting in high retooling costs.
The improved method of the present invention for inserting studs into a strip employs the techiques of ultrasonic welding. Ultrasonic welding is a process whereby the material composing the strip is excited by ultrasonic energy to its melting point. The melted or deformed material then flows around and engages a stud to be inserted under the influence of natural or applied forces. As the ultrasonic energy is removed, the temperature of the material recedes from its melting point, thereby returning to its solid phase, and firmly retaining the stud within the strip.
However, the utilization of ultrasonic welding by the methods of the prior art has some drawbacks, making it unattractive for some applications. Specifically, the prior art methods utilizing ultrasonic welding require a hole or other aperture of sufficient size to accept and stud to be pre-formed in the strip or segment of plastic material. Some methods require the addition of an insert into the pre-formed hole and ultrasonically welding to the aperture walls. The stud would then be inserted into the pre-formed hole. The step of pre-forming the hole makes these methods time consuming and labor intensive, leading to greater costs. Additionally, the requirement of the insert adds to the cost of utilizing these methods.
The stud and the method of ultrasonic insertion of articles into a trip or segment as provided by the present invention eliminates many of the drawbacks present in the prior art.